Collect paired data values for the two variables
Compute the mean of each variable
Subtract each mean from its corresponding values to get deviations
Multiply each pair of deviations
Sum all the products of deviations
Compute the sum of squared deviations for each variable
Take the square root of the product of the two sums of squared deviations
Divide the sum of products of deviations by the square root result
Use the formula: r = Σ[(x – xÌ„)(y – ȳ)] / √[Σ(x – xÌ„)² Σ(y – ȳ)²]
Verify that the result lies between -1 and 1